This invention relates generally to apparatus for aiding the landing of aircraft, and more particularly to glide slope control apparatus for use with a visual approach to the runway.
The capability of using small and limited landing areas is required for numerous operations of military aircraft, including short take-off and landing (STOL) transport planes as well as fighter planes. Landing under such conditions is possible only if the final approach takes place under almost optimal conditions of the mechanics of flight, i.e., if the glide angle, the angle of pitch and the speed are so adjusted that flattening-out and rolling-out after touchdown is effected within the shortest possible distance.
With modern military aircraft, the estimating capability of the pilot is frequently inadequate to safely land the aircraft thereby necessitating aiding devices aboard the plane. One such device is a glide slope control. The glide slope control provides information to the pilot concerning the aircraft's position relative to an optimum glidepath that will assure a safe descending approach angle and a proper touchdown on the runway.
Often the requirement for STOL aircraft is dictated by the airfield being located relatively close to enemy territory or by the airfield being located in a remote area where only austere conditions are present. Oftentimes, too, a requirement will exist for special operational aircrews to perform night landings at airfields under less then optimal conditions. These night operations sometimes require radio and electromagnetic silence and place an excessive burden on the visual capability of the pilot. Under such circumstances, a non-electromagnetic technique is sorely needed to provide precise glide slope performance of the aircraft for both cockpit and ground monitoring during approach to landing. In addition, such a technique is needed to provide substantive training of personnel and to provide suitable operating conditions for research and development of future products.
Prior work in the area of optical glide slope techniques include U.S. Pat. No. 2,597,321 to R. C. Hergenrother which discloses a light ray, projected from ground sources, used to determine the aircraft approach angle for gliding the plane into a proper landing. Also, U.S. Pat. No. 2,489,222 to Herbold teaches a glide slope indicator system which uses a ground based light source and receptive photodiodes positioned on the aircraft. While these patents are suitable for their intended purpose, neither patent exhibits the simplicity and inexpensiveness of the present invention nor does either patent provide the degree of precision desired for nighttime and other critical landing operations.